Bjerselius, Rickard

Mayer, Ian

Kindhal, Hans

Abstract [en]

The behavioral responses to urine and ovarian fluids from conspecific and heterospecific ovulated females were studied in mature Atlantic salmon (Salmo salar) male parr in a two-choice fluviarium. The males reacted differently to the stimulants. They spent more time in water scented by urine from salmon or brown trout (Salmo trutta L.) females compared to the time in water with ovarian fluids from salmon females. Furthermore, the males were attracted to salmon female urine (different from an indifferent reaction). Males exposed to urine of either species had higher plasma concentrations of testosterone (T) compared to unexposed controls. Measurement of the concentrations of prostaglandin F-2alpha (PGF(2alpha)) and its major metabolite 15-ketodihydroprostaglandin F-2alpha (15-ketodihydro-PGF(2alpha)) showed that the concentrations of the substances were higher in ovarian fluids of both species compared to those in urine. PGF(2alpha) showed a greater difference between ovarian fluid and urine than its major metabolite. The results suggest that urine of both species, in contrast to ovarian fluid, contain substances that attract mature Atlantic salmon male parr and that the active substances are neither PGF(2alpha) nor 15-keto-PGF(2alpha).